Separation method for potassium from aqueous koh solutions

ABSTRACT

The process described herein demonstrates a more efficient and effective way to remove certain chemicals from industrial waste water. Specifically, the invention set forth demonstrates a method comprised of at least two steps in which up to 96% of potassium can be removed from an aqueous solution comprising potassium hydroxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Non-Provisional Patent Application, filed under 35 U.S.C. 5 111(a),claims the benefit under 35 U.S.C. 5 119(e)(1) of U.S. ProvisionalPatent Application No. 61/742,572, filed under 35 U.S.C. 5 111(b) on 14Aug. 2012, and which is hereby incorporated by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention was made by an agency of the United States Government orunder a contract with an agency of the United States Government. Thename of the U.S. Government agency and the Government contract numberare: B&W Technical Services Y-12, contract 4300074126.

BACKGROUND

1. Field

The invention disclosed herein the method for separating potassium fromaqueous potassium hydroxide solution.

2. Description of Related Art

In an increasingly environmental conscious world, one problem that hascontinued to plague industry and government is how to remove certainharmful chemicals from industrial waste water. One of those noxiouschemicals is potassium. There have been attempts to develop a processthat is effective. Neumann in U.S. Pat. No. 3,773,902 (1973) for exampleset forth a method to remove potassium but reported that up to 66% ofthe potassium would remain in the solution after treatment and that theprocess was continuous in nature.

BRIEF SUMMARY OF THE INVENTION

The instant invention is a dramatic improvement of the previously knownart. This process as a whole separates between about 50 to about 96% ofpotassium from an aqueous potassium hydroxide (KOH) solution (i.e., KOHdissolved in water). The process is a two-step process. The first stepof the process (step 1) is similar, though not identical, to that whichwas previously reported by Neumann. However, the first step of thecurrent process has been improved to yield greater separation comparedto the prior process. The second step (step 2), coupled to the firststep, results in a very efficient precipitation of potassium. Thisprocess (steps 1 & 2) is useful for any industry that generatesconcentrated potassium hydroxide solutions as waste. In addition, theend product of the process, potassium carbonate sesquihydrate, is usefulfor any industry that uses potassium carbonate.

The second step in the process itself is unique. The uniqueness of thisprocess lies in the utilization of nucleation facility for thecrystallized solid byproduct. The precipitation of potassium from thewaste stream in the form of solid byproduct can only be practicallyapplied as described in this narrative. Previously reported process wasa continuous process as opposed to the current process, a batch process,which is better-suited for slow accumulation and treatment afterincreasing time intervals.

In one embodiment, a method of removing potassium from an aqueoussolution comprising potassium hydroxide is provided, the methodcomprising: 1) placing a volume of said aqueous solution comprisingpotassium hydroxide into a container, said container comprising a—Si—O—Si— network, and then bubbling carbon dioxide gas though saidvolume of aqueous solution comprising potassium hydroxide; 2) adding tosaid volume of aqueous solution comprising potassium hydroxide from step1), and relative to said volume of aqueous solution comprising potassiumhydroxide, about one-half to about one volume of (C₁-C₅)-OH alcohol; and3) separating precipitate from the solution of step 2).

In one embodiment, the container is a glass container or a quartzcontainer.

In one embodiment, the bubbling is performed for between about 1 andabout 24 hours.

In one embodiment, the bubbling is performed for about 3 hours.

In one embodiment, about one-half volume of (C₁-C₅)-OH alcohol is addedin step 2).

In one embodiment, about one volume of (C₁-C₅)-OH alcohol is added instep 2).

In one embodiment, the (C₁-C₅)-OH alcohol is selected from the groupconsisting of methanol, ethanol, and isopropanol.

In one embodiment, the (C₁-C₅)-OH alcohol is ethanol.

In one embodiment, the bubbling is performed at a pressure between about1 and about 5 atmospheres.

In one embodiment, the bubbling is performed at a pressure greater thanatmospheric pressure.

In one embodiment, the pH of the volume of said aqueous solutioncomprising potassium hydroxide, before bubbling said carbon dioxide gasthough said volume, is between about 12.5 and 13.5, and after bubblingsaid carbon dioxide gas though said volume is between about 6 and about8.

In one embodiment, the pH of the volume of said aqueous solutioncomprising potassium hydroxide, before bubbling said carbon dioxide gasthough said volume, is about 13, and after bubbling said carbon dioxidegas though said volume is between about 7 and about 8.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature, objects, and advantages ofthe present disclosure, reference should be had to the followingdetailed description, read in conjunction with the following drawings,wherein like reference numerals denote like elements.

FIG. 1 is a schematic drawing of the separation process.

FIG. 2 shows the mother liquor after the first step of bubbling with CO₂gas in a glass container.

FIG. 3 shows the formation of potassium carbonate solid (whiteprecipitate) after alcohol treatment in step 2.

DETAILED DESCRIPTION

Before the subject disclosure is further described, it is to beunderstood that the disclosure is not limited to the particularembodiments of the disclosure described below, as variations of theparticular embodiments may be made and still fall within the scope ofthe appended claims. It is also to be understood that the terminologyemployed is for the purpose of describing particular embodiments, and isnot intended to be limiting. Instead, the scope of the presentdisclosure will be established by the appended claims.

In this specification and the appended claims, the singular forms “a,”“an,” and “the” include plural reference unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood to one of ordinary skill in the art to which this inventionbelongs.

Applicant determined experimentally that the material of the reactionvessel plays a role in the efficiency and separation of the solidproduct. A glass container, for example, contributes to improvedpotassium-containing crystal formation and more efficient separation ofthe potassium-carbonate solids. Glass, among other substances, comprisesa —Si—O—Si— network due to the presence of silicon dioxide (SiO₂), alsocalled silica. Without wishing to be bound by theory, Applicanthypothesizes that the dangling —OH and Si═O functional groups on thesurface of substances comprising a —Si—O—Si— network induce improvednucleation of the potassium-carbonate crystals, thereby improving theefficacy of the crystal-forming reaction. Thus, containers made of,containing, or comprising substances including, but not limited to thefollowing could be used in the instant methods: fused silica glass, sodalime glass, sodium borosilicate glass, lead-oxide glass, aluminosilicateglass, recycled glass, quartz, and combinations thereof.

In one embodiment of the instant method, step 1 is the bubbling of a 50%aqueous KOH solution (50% w/v KOH, in water) contained in a glass vesselwith a stream of carbon dioxide (CO₂) gas from a pressurized cylinder.The bubbling is done at atmospheric pressure. A three hour bubblingtreatment of carbon dioxide yields a crystalline solid (potassiumcarbonate sesquihydrate, K₂CO₃.1.5 H₂O) and some remaining potassiumcarbonate (K₂CO₃) dissolved in the initial liquor solution (see FIG. 1).The potassium carbonate sesquihydrate solid can be separated by, forexample, filtration, settling, or centrifugation. At the end of step 1,about 63% of the initial potassium is removed from the 50% aqueous KOHsolution.

Step 2 of the instant method comprises treatment of the solution fromstep 1 with about one-half volume to about an equal volume of ethanol orother suitable (C₁-C₅)-OH solvent. The addition of ethanol, for example,to the remaining mixture lowers the solubility of the remainingpotassium carbonate, causing additional potassium carbonate crystals toform and precipitate out of solution. This method is unique andunexpected because alcohol is practically immiscible with an aqueouspotassium carbonate solution (i.e., a solution prepared from water andpotassium carbonate). In this case, however, they mix because the motherliquor from step 1 comprises not only potassium carbonate but alsobicarbonate ions (e.g., KHCO₃).

At the end of step 2, about 77% of the remaining dissolved potassium istransformed into precipitate and can be removed from the initialsolution by filtration, settling, centrifugation, or any other techniquecommonly known to those of ordinary skill in the art. The overallseparation efficiency of the two step method is such that about 91% ofthe potassium is removed from an initial solution of 50% aqueouspotassium hydroxide.

EXAMPLE 1

KOH Waste Stream Treatment

From a pressurized CO₂ cylinder, via a manifold, three batches (200 mL,1 L, and 3 L) of a waste KOH sample were bubbled for three hours. Thisstep of the treatment process was exothermic. From room temperature, thetemperatures of the batches rose to 41°, 39° and 31° C. for the 200 mL,1 L and 3 L volumes, respectively. The pH of the original waste streamwas about 13, and after bubbling with CO₂ the final pH of the treatedbatches was between about 7 and about 8. In the original method, whichwas developed with an aqueous potassium hydroxide solution of 50%concentration, a majority of the potassium would separate as acrystalline solid material (potassium carbonate sesquihydrate) at thisstep. Here, using an actual waste sample, no crystalline materials wereseparated at this point. This is reasonable and expected because theoriginal method was developed using an aqueous potassium hydroxidesolution of 50% concentration. By contrast, the actual waste sample hada potassium concentration of 10.6% (as determined by laboratoryanalysis). After completion of the first step, a one-half volume ofethanol was added to each of the samples, as described above, and theprecipitate allowed to form. The second step of the process removedabout 50 to about 60% of potassium from the samples (as compared to thestarting potassium concentration). The solid samples were analyzed byX-ray powder diffraction (XRD) method, and were identified as potassiumbicarbonate (KHCO3) instead of potassium carbonate sesquihydrate(K₂CO₃.1.5H₂O). Although different forms of the compound with preferredorientation were detected, no other minor or intermediate constituentswere detected.

The effectiveness of the second step was unexpected because when a purewater/potassium carbonate solution is treated with ethanol, the solutionremains unchanged and immiscible. Here however, treating the CO₂-treatedpotassium sample (step 1) with a one-half volume of ethanol (step 2)allowed separation of about 50 to about 60% of the potassium from wastesamples containing 10.6% potassium.

All references cited in this specification are herein incorporated byreference as though each reference was specifically and individuallyindicated to be incorporated by reference. The citation of any referenceis for its disclosure prior to the filing date and should not beconstrued as an admission that the present disclosure is not entitled toantedate such reference by virtue of prior invention.

It will be understood that each of the elements described above, or twoor more together may also find a useful application in other types ofmethods differing from the type described above. Without furtheranalysis, the foregoing will so fully reveal the gist of the presentdisclosure that others can, by applying current knowledge, readily adaptit for various applications without omitting features that, from thestandpoint of prior art, fairly constitute essential characteristics ofthe generic or specific aspects of this disclosure set forth in theappended claims. The foregoing embodiments are presented by way ofexample only; the scope of the present disclosure is to be limited onlyby the following claims.

What is claimed is:
 1. A method of separating potassium from an aqueoussolution comprising potassium hydroxide, the method comprising: 1)placing a volume of said aqueous solution comprising potassium hydroxideinto a container, said container comprising a —Si—O—Si— network, andthen bubbling carbon dioxide gas though said volume of aqueous solutioncomprising potassium hydroxide; 2) adding to said volume of aqueoussolution comprising potassium hydroxide from step 1), and relative tosaid volume of aqueous solution comprising potassium hydroxide, aboutone-half to about one volume of (C₁-C₅)—OH alcohol; and 3) separatingprecipitate from the solution of step 2).
 2. The method of claim 1,wherein the container is a glass container or a quartz container.
 3. Themethod of claim 1, wherein the bubbling is performed for between about 1and about 24 hours.
 4. The method of claim 1, wherein the bubbling isperformed for about 3 hours.
 5. The method of claim 1, wherein aboutone-half volume of (C₁-C₅)—OH alcohol is added in step 2).
 6. The methodof claim 1, wherein about one volume of (C₁-C₅)—OH alcohol is added instep 2).
 7. The method of claim 1, wherein the (C₁-0 ₅)-OH alcohol isselected from the group consisting of methanol, ethanol, andisopropanol.
 8. The method of claim 1, wherein the (C₁-C₅)—OH alcohol isethanol.
 9. The method of claim 1, wherein the bubbling is performed ata pressure between about 1 and about 5 atmospheres.
 10. The method ofclaim 1, wherein the bubbling is performed at a pressure greater thanatmospheric pressure.
 11. The method of claim 1, wherein the pH of thevolume of said aqueous solution comprising potassium hydroxide, beforebubbling said carbon dioxide gas though said volume, is between about12.5 and 13.5, and after bubbling said carbon dioxide gas though saidvolume is between about 6 and about
 8. 12. The method of claim 1,wherein the pH of the volume of said aqueous solution comprisingpotassium hydroxide, before bubbling said carbon dioxide gas though saidvolume, is about 13, and after bubbling said carbon dioxide gas thoughsaid volume is between about 7 and about
 8. 13. The method of claim 1,wherein the amount of potassium in the precipitate of step 3) is atleast about 50% of the amount of potassium in the aqueous solutioncomprising potassium hydroxide of step 1), before bubbling with carbondioxide.
 14. The method of claim 1, wherein the amount of potassium inthe precipitate of step 3) is at least about 60% of the amount ofpotassium in the aqueous solution comprising potassium hydroxide of step1), before bubbling with carbon dioxide.
 15. The method of claim 1,wherein the amount of potassium in the precipitate of step 3) is atleast about 80% of the amount of potassium in the aqueous solutioncomprising potassium hydroxide of step 1), before bubbling with carbondioxide.
 16. The method of claim 1, wherein the amount of potassium inthe precipitate of step 3) is at least about 90% of the amount ofpotassium in the aqueous solution comprising potassium hydroxide of step1), before bubbling with carbon dioxide.
 17. The method of claim 1,wherein the amount of potassium in the precipitate of step 3) is atleast about 96% of the amount of potassium in the aqueous solutioncomprising potassium hydroxide of step 1), before bubbling with carbondioxide.
 18. A method of separating potassium from an aqueous solutioncomprising potassium hydroxide, the method comprising: 1) placing avolume of said aqueous solution comprising potassium hydroxide into acontainer, said container comprising a —Si—O—Si— network, and thenbubbling carbon dioxide gas though said volume of aqueous solutioncomprising potassium hydroxide; 2) adding to said volume of aqueoussolution comprising potassium hydroxide from step 1), and relative tosaid volume of aqueous solution comprising potassium hydroxide, aboutone-half to about one volume of (C₁-C₅)—OH alcohol; and 3) separatingprecipitate from the solution of step 2), wherein: a) the container is aglass container or a quartz container; b) the bubbling is performed forbetween about 1 and about 24 hours; c) wherein the (C₁-C₅)—OH alcohol isselected from the group consisting of methanol, ethanol, andisopropanol; d) wherein the bubbling is performed at a pressure betweenabout 1 and about 5 atmospheres; e) wherein the pH of the volume of saidaqueous solution comprising potassium hydroxide, before bubbling saidcarbon dioxide gas though said volume, is between about 12.5 and 13.5,and after bubbling said carbon dioxide gas though said volume is betweenabout 6 and about 8; and f) wherein the amount of potassium in theprecipitate of step 3) is at least about 50% of the amount of potassiumin the aqueous solution comprising potassium hydroxide of step 1),before bubbling with carbon dioxide.
 19. The method of claim 18, whereinthe amount of potassium in the precipitate of step 3) is at least about96% of the amount of potassium in the aqueous solution comprisingpotassium hydroxide of step 1), before bubbling with carbon dioxide 20.A method of separating potassium from an aqueous solution comprisingpotassium hydroxide, the method comprising: 1) placing a volume of saidaqueous solution comprising potassium hydroxide into a container, saidcontainer comprising a —Si—O—Si— network, and then bubbling carbondioxide gas though said volume of aqueous solution comprising potassiumhydroxide; 2) adding to said volume of aqueous solution comprisingpotassium hydroxide from step 1), and relative to said volume of aqueoussolution comprising potassium hydroxide, about one-half volume of(C₁-C₅)—OH alcohol; and 3) separating precipitate from the solution ofstep 2), wherein: a) the container is a glass container container; b)the bubbling is performed for about 3 hours; c) wherein the (C₁-C₅)—OHalcohol is ethanol; d) wherein the bubbling is performed at a pressureof about 1 atmosphere; e) wherein the pH of the volume of said aqueoussolution comprising potassium hydroxide, before bubbling said carbondioxide gas though said volume, is about 13, and after bubbling saidcarbon dioxide gas though said volume is between about 7 and about 8;and f) wherein the amount of potassium in the precipitate of step 3) isat least about 60% of the amount of potassium in the aqueous solutioncomprising potassium hydroxide of step 1), before bubbling with carbondioxide.